I bought a 66 mustang coupe w/ I6 C4 trans. It has the cruisomatic trans. When I place the gear selctor in either gear ( except for Low 1) drive gears the trans pulls out in 2nd gear and as soon as the rpms build it downshifts to 1st then back to second. If I manually shift thru all the gears they work in order. When I place the gear shift in drive or the green dot position it always pulls out in 2nd then shortly afterward downshifts to 1st then quickly back to 2nd. I replaced the modulator valve, checked the vaccum tube and hose for any leaks, and adjusted the kick down cable. I know this might sound stupid , but shouldnt this car pull out in 1st gear , then go to 2nd, 3rd? the gears have never slipped or acted badly , just isnt shifting in order. Any suggestions? check the valve body? change the filter and fluid? adjust bands?

 

Sounds like it is working the way Ford designed it. The tranny starts out in 2nd gear. This is controlled by the valve body inside the tranny. If you get a valve body from a 68 or 69, there might be some other years that work. Then it will start out in 1st gear. Do a search C4 green dot, I'm sure you will find out more info. Good luck.
Lowell